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(i) Name the nematode… (Class 12 Biology 2024, Q31b)

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BiologyCBSE Class 12 · Board exam 2024, set 57/5/1 · 5 marks · Long answer

CBSE Class 12 Biology 2024: question 31(b)

Set in the CBSE Class 12 board exam of 2024, paper 57/5/1, section E, question 31(b), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q31(b) · 5 marks · Long answerBiotechnology and its Applications

(i) Name the nematode (scientific name) that infects the roots of tobacco plant and reduces its yield.
(ii) Name the vector that is used to introduce nematode-specific genes into the host plant (tobacco).
(iii) How do sense and anti-sense RNAs function ?
(iv) Why could parasite not survive in a transgenic tobacco plant ?

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 57/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

The nematode is a root-knot nematode named in NCERT.

Hint 2

Which bacterium is a natural genetic engineer of plants?

Hint 3

What happens when two complementary RNA strands meet inside a cell?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (i) The nematode is Meloidogyne incognita.

    1 mark

  2. (ii) The vector is Agrobacterium tumefaciens (its Ti plasmid).

    1 mark

  3. (iii) Nematode-specific genes are introduced so that the plant produces both sense and anti-sense RNA. The two are complementary to each other.

    1 mark

  4. (iii) Being complementary, they pair to form double-stranded RNA (dsRNA), which initiates RNA interference (RNAi).

    1 mark

  5. (iv) The dsRNA binds to the specific mRNA of the nematode and silences it.

    ½ mark

  6. (iv) This prevents translation of that mRNA, so the parasite cannot survive in the transgenic host.

    ½ mark

Answer: (i) Meloidogyne incognita. (ii) Agrobacterium tumefaciens (Ti plasmid). (iii) Sense and anti-sense RNA are complementary and form dsRNA, which starts RNAi. (iv) The dsRNA silences the nematode's specific mRNA, preventing its translation, so the parasite dies.

Where the marks are

  • Meloidogyne incognita (1 mark)
  • Agrobacterium tumefaciens (1 mark)
  • Sense and anti-sense RNA are complementary (1 mark) and form dsRNA (1 mark)
  • dsRNA binds the specific mRNA (½ mark) and prevents its translation, silencing it (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Biotechnology and its Applications, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 57/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.